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Improving tribological properties of sputtered boron carbide coatings by process modifications

: Eckardt, T.; Bewilogua, K.; Kolk, G.J. van der; Hurkmans, T.; Trinh, T.; Fleischer, W.


Surface and coatings technology 126 (2000), Nr.1, S.69-75
ISSN: 0257-8972
Fraunhofer IST ()
boron carbide coatings; tribological property; low friction; reactive sputtering; structural modification; PVD

Boron carbide coatings are well-known for extreme hardness and excellent wear resistance. In this paper a d.c. magnetron sputter process for the deposition of boron carbide coatings is described. It is shown that by adding small amounts of a hydrocarbon reactive gas ( in this case acetylene) the coefficient of friction can be reduced from 0.8 down to 0.2. Results from a laboratory scale deposition device are successfully transferred to an industrial batch coater. The coating adhesion is well enhanced by a titanium interlayer. From the analysis of the chemical composition and from hardness values it is concluded that a structural modification is responsible for the improvement of sliding behaviour. It is suggested that the introduction of additional bondings reduces the brittleness of boron carbide. Furthermore, a comparison with metal-containing amorphous carbon coatings (Me-DLC) reveals several similarities.